Using a single vehicle with multiple removable attachment devices to perform a variety of ground working functions is more cost effective than using separate specialized machines for each function. Thus, several devices for attachment to a self-propelled vehicle, including cold planers and rock wheels, have been developed. These attachments are powered by connecting them to the vehicle's hydraulic power source.
Some cold planers, such as the AP 400 Series II offered by DigTec of Columbia, S.C., are capable of providing hydraulic control for side shift, depth and tilt adjustments. Each of these adjustments is controlled by separate hydraulic cylinders and hydraulic circuits. Thus, there are three separate hydraulic control mechanisms accessible to the operator to control such a cold planer. In the AP Series II by DigTec, three levers are provided outside the cab of the vehicle in front of the operator. This is undesirable as the operator must reach out from the protective confines of the cab to activate the controls. Furthermore, the presence of six (6) hydraulic cables, two for each positioning hydraulic cylinder, proximate the control levers increases the potential for injury to the operator from accidental rupture or contact with the cables, which can, under normal operation, reach temperatures of over 200 degrees Fahrenheit. Moreover, excessive time is required to connect and disconnect the six hydraulic cables from the vehicle each time a different attachment is mounted to the vehicle. Thus, it is desirable to provide a hydraulic control system for movement in many dimensions, such as tilt, side shift and depth, which reduces the potential for injury to the operator. The planer positioning hydraulic controls of the DigTec planer are also hand-actuated. Since both hands of an operator are usually occupied by the vehicle movement controls, the operator cannot simultaneously control the vehicle movement and adjust the position of the cold planer with the hydraulic positioning controls. Furthermore, it is desireable to limit the number of hydraulic systems or subsystems required to provide such control in order to reduce manufacturing cost and the number of parts that might break down.
The pavement planing machine disclosed in U.S. Pat. No. 4,878,713 has both tilt adjustment and a side shift adjustment for a cold planer which is mountable to a skid-steer front end loader. Control for both adjustments is accomplished by using a single hydraulic cylinder actuable by a foot pedal in the vehicle cab. However, this planing machine does not allow for hydraulic depth control of the machine, nor are multiple hydraulic cylinders operated by a single hydraulic circuit.